IN AQUEOUS SOLUTION, AND THE EXISTENCE OF COMPLEX TONS. 
125 
Certain regularities in the behaviour of the ditfereiit jellies used may Ije noted. 
Good firm jellies suitable for use in the experiments are obtained witli the 
following salts, using 12 per cent, gelatine : Potassium chloride, bromide, fluoride, and 
chromate, sodium acetate, the sulj^hates of magnesium, copper, and cadmium, and 
half-normal silver nitrate. 
To obtain a sufficiently solid jelly of lithium or magnesium cldoride, it is necessary 
to use 20 per cent, gelatine. 
0'5 N potassium iodide and 2'0 N cadmium Ijromide, do not form solid jellies even 
with 23 and 25 per cent, of gelatine. 
It is not possible to prejxire aO‘5N aluminium sulphate jelly containing 12 per 
cent, gelatine, as it becomes coagulated and semi-solid even at 100°; with 5 per cent, 
gelatine a good solution is obtained, which solidifies to a very fine jelly of liigh melting 
point. 
By the electrolytic formation of the following gelatine solutions, the jellies are 
melted even with very small heating by the current 
Copper or magnesium nitrate formed by the passage of N(d 3 anion into 12 per cent, 
jellies of 2 N copper or magnesium sulphate. In only one experiment the copper 
nitrate jelly so formed was not melted. 
The passage of Br ions into a lithium chloride jelly results in its melting with a 
current density winch would be quite safe, Avith no formation of lithium bromide. 
The entrance of bichromate ions into a lithium chloride jelly invariably occasions 
the melting of the latter; and H or OH ions, so dilute as 0’2 N, immediately destroy 
any jelly they enter. 
From tliese observations, wdiich are entirely qualitative, the statement seems to be 
justified that the influence of the salt on the melting point of a jelly depends on the 
nature of the ions, tliat, among anions the low^ering effect increases as we })ass down 
the series SO^, Cl, Br, to NOg, Cr^O^ and 1, and similarly for the cations as we pass 
down the series K, Na, Cu, Cd, Li, and Mg. 
The sulphates of all these readily form jellies ol high melting point; Avith the 
chloiides the melting point falls as Ave pass from potassium’ and sodium to Mg, and 
so for the others. A quantitative investigation of the influence of salts oii the 
melting points of gelatine solutions should yield instructiAm and interesting results. 
As indicators, normal solutions of the folioAving salts have been used :— 
Cation Indicators. 
CuSOj, Avith copper anode, to minimise the formation of H ions. 
CdSO^., with cadmium anode. 
LiCl, Avith LioCOg suspended in the solution. 
* This difficulty of the melting of the gehitiiie would be OA’crcoiue by substituting mu ciirthcuwai'c 
partition, as has been done for the acids and alkalies. 
